Gas Analyzers Gas Analyzers are laboratory instruments that measure and display the concentration of a gas. An Oxygen Analyzer measures and displays the concentration of Oxygen (O2). A Carbon Dioxide Analyzer measures and displays the concentration of Carbon Dioxide (CO2). AEI Technologies’ S-3A Oxygen Analyzer and CD-3A Carbon Dioxide Analyzer are the Gold Standard in respiratory gas analysis. These respiratory gas analyzers have been trusted by thousands of institutions worldwide for over 45 years as THE O2 and CO2 gas measurement Gold Standards for their laboratories.